Reference is made to commonly-assigned, U.S. patent application Ser. No. 09/114,022, filed Jul. 10, 1998, now U.S. Pat. No. 6,045,917.
This invention relates to an ink jet recording element, more particularly to an inkjet recording element which contains particles.
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An inkjet recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-forming layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
While a wide variety of different types of image-recording elements for use with ink jet devices have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness. The requirements for an image recording medium or element for ink jet recording are very demanding.
It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, an ink jet recording element must:
Be readily wetted so there is no puddling, i.e., coalescence of adjacent ink dots, which leads to nonuniform density
Exhibit no image bleeding
Exhibit the ability to absorb high concentrations of ink and dry quickly to avoid elements blocking together when stacked against subsequent prints or other surfaces
Provide a high level of gloss and avoid differential gloss
Exhibit no discontinuities or defects due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like
Not allow unabsorbed dyes to aggregate at the free surface causing dye crystallization, which results in bloom or bronzing effects in the imaged areas
Have an optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light
U.S. Pat. No. 5,027,131 relates to an ink jet recording element comprising a support having thereon an ink-retaining layer and an ink transporting layer. The ink transporting layer is porous and contains particles in a large amount. This layer is designed to allow ink to be transported through it to the ink retaining-layer. However, there is a problem with this element in that it is a reverse-viewing element. In other words, the support has to be transparent in order to view the image through it. Opaque supports such as paper are therefore excluded by this technique.
EP 0 888 902 relates to an ink jet recording element comprising an ink sorptive layer which contains up to 15% by weight of polymer particles. However, there is a problem with this element in that the surface layer is not smooth and scatters light.
It is an object of this invention to provide an ink jet recording element which does not require a transparent support. It is another object of this invention to provide an ink jet recording element that has a glossy surface. It is another object of this invention to provide an ink jet recording element that has an improved waterfastness.
This and other objects are provided by the present invention comprising an ink jet recording element comprising a support having thereon, in the order recited, a base layer comprising a hydrophilic material and a non-porous, ink-receptive top layer comprising a binder, mordant and polymeric particles, the particles having a particle size of less than about 0.5 xcexcm and being present in an amount of from about 20 to about 50% by weight of the ink-receptive top layer.
Another embodiment of the invention relates to an ink jet printing process comprising:
a) providing an ink jet recording element as described above, and
b) applying liquid ink droplets thereon in an image-wise manner.
By use of the invention, ink jet recording elements are obtained which do not require a transparent support, have a glossy surface and improved waterfastness.
The polymeric particles useful in the top layer of the ink jet recording element of the invention may be made from virtually any polymer and can be synthesized, for example; from the following monomers: alkyl esters of acrylic or methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate; the hydroxyalkyl esters of the same acids such as 2-hydroxyethyl acrylate, and the nitrile and amides of the same acids such as acrylonitrile, methacrylonitrile, and butyl acrylamide, vinyl acetate, vinylidene chloride, vinyl chloride, and vinyl aromatic compounds such as styrene, ethyl vinyl benzene, vinyl toluene, dialkyl maleates, dialkyl itaconates, dialkyl malonates, isoprene, and butadiene. Crosslinking and grafting monomers which may be used together with the foregoing monomers to crosslink the polymeric particles are polyfunctional with respect to the polymerization reaction, and may include, for example, esters of unsaturated monohydric alcohols with unsaturated monocarboxylic acids, such as allyl methacrylate, and vinyl methacrylate, esters of saturated glycols or diols with unsaturated monocarboxylic acids, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and polyfunctional aromatic compounds such as divinyl benzene.
In a preferred embodiment of the invention, the polymeric particles are made from acrylic or styrenic monomers, such as poly(methyl methacrylate) or polystyrene. In another preferred embodiment, the polymeric particles are crosslinked.
Following are examples of polymeric particles which may be used in the invention:
The addition of the mordant to the top layer does not degrade other performance features such as dry time, lightfastness, coalescence, bleeding, adhesion of the layers, waterfastness, and gloss when printed with a variety of ink jet inks.
Preferred mordant polymers used in the invention comprise units having the formula: 
wherein:
A represents units of an addition polymerizable monomer containing at least two ethylenically unsaturated groups;
B represents units of a copolymerizable, xcex1,xcex2-ethylenically unsaturated monomer;
Q is nitrogen or phosphorous;
R1, R2 and R3 each independently represents a carbocyclic or alkyl group;
Mxe2x88x92 is an anion;
x is from about 0.25 to about 5 mole percent;
y is from about 0 to about 90 mole percent; and
z is from about 10 to about 99 mole percent.
In a preferred embodiment of the invention, A is a repeating unit of an addition polymerizable monomer containing at least two ethylenically unsaturated groups, such as vinyl groups generally having the following structure: 
wherein:
n is from 1 to about 10, preferably 2 or 3;
each R4 independently represents hydrogen or methyl; and
R5 is a linking group comprising one or more condensation linkages such as amide, sulfonamide, esters such as sulfonic acid ester, arylene etc., or a condensation linkage and an organic nucleus such as alkylene, e.g., methylene, ethylene, trimethylene, arylene, etc.
Suitable monomers from which the repeating units of A are formed include divinylbenzene, allyl acrylate, allyl methacrylate, N-allylmethacrylamide, etc.
B in the above formula is a unit of a copolymerizable xcex1,xcex2-ethylenically unsaturated monomer (including two, three or more repeating units), such as ethylene, propylene, 1-butene, isobutene, 2-methylpentene, etc. A preferred class of ethylenically unsaturated monomers which may be used include the lower 1-alkenes having from 1 to about 6 carbon atoms; styrene, and tetramethylbutadiene and methyl methacrylate.
R1, R2 and R3 in the above formula each independently represents a carbocyclic group such as aryl, aralkyl, and cycloalkyl such as benzyl, phenyl, p-methyl-benzyl, cyclohexyl, cyclopentyl, etc.; or an alkyl group preferably containing from 1 to about 20 carbon atoms such as methyl, ethyl, propyl, isobutyl, pentyl, hexyl, heptyl, decyl, etc. In a preferred embodiment, R1, and R2 are each methyl, R3 is benzyl, Q is nitrogen, A is divinylbenzene, and B is styrene.
Mxe2x88x92 in the above formula is an anion, i.e., a negative salt forming an ionic radical or atom such as a halide, e.g., bromide or chloride, sulfate, alkyl sulfate, alkane or arene sulfonate, acetate, phosphate, etc.
Further examples of the mordant polymers useful in the invention and preparation of the above polymers are found in U.S. Pat. No. 3,958,995, the disclosure of which is hereby incorporated by reference. Specific examples of the major components of such mordant polymers include the following:
The mordant in the top layer may be used in any amount effective for intended purpose. In general, good results have been obtained when the mordant polymer is present in an amount of about 5% to about 25% by weight of the top layer, preferably about 10%.
Binders useful in the top layer of the recording element of the invention include nonionic cellulose ethers, anionic cellulose ethers, polyvinyl alcohol, sulfonated polyesters, polyvinylpyrrolidone, methyl cellulose, e.g., A4M (Dow Chemical Co.) and hydroxyethyl cellulose, such as JR400 (hydroxyethyl cellulose reacted with a trimethyl ammonium chloride substituted epoxide from Amerchol Corp.) in a weight ratio of 80/20. These materials may be used in amounts from about 0.75 g/m2 to about 1.25 g/m2, preferably from about 1 g/m2 to about 1.1 g/m2. The top layer generally has a thickness of about 0.1 to about 2.0 xcexcm.
In a preferred embodiment of the invention, the binder is a hydroxyethyl cellulose cationically-modified cellulose ether. In another preferred embodiment, the cationically modified cellulose ether is a hydroxyethyl cellulose reacted with trimethylammonium chloride substituted epoxide or hydroxyethyl cellulose reacted with a dodecyl dimethylammonium chloride substituted epoxide, as described in copending Ser. No. 08/763,808, of Shaw-Klein et al., filed Dec. 11, 1996.
The top layer may contain about 5 to about 75 weight percent of the cationically-modified cellulose ether described above. Useful cationically-modified cellulose ether polymers include Celquat(copyright) SC240C (hydroxyethyl cellulose reacted with trimethylammonium chloride substituted epoxide from National Starch and Chemical Co.) and Quatrisoft(copyright) LM-200 (hydroxyethyl cellulose reacted with a dodecyl dimethylammonium chloride substituted epoxide from Amerchol Corp.).
The base layer is primarily intended to act as a sponge layer for the absorption of ink solvent. As such, it is primarily composed of hydrophilic or porous materials. Generally, the base layer has a thickness of about 3 to about 20 Jim, and is present in an amount from about 5 g/m2 to about 7 g/m2, preferably from about 5.3 g/m2 to about 5.5 g/m2. Suitable hydrophilic materials include gelatin, acetylated gelatin, phthalated gelatin, oxidized gelatin, chitosan, poly(alkylene oxide), poly(vinyl alcohol), modified poly(vinyl alcohol), sulfonated polyester, partially hydrolyzed poly(vinylacetate/vinyl alcohol), poly(acrylic acid), poly(1-vinylpyrrolidone), poly(sodium styrene sulfonate), poly(2-acrylamido-2-methane sulfonic acid), or polyacrylamide or mixtures thereof. Copolymers of these polymers with hydrophobic monomers may also be used.
The pH of the base layer may be adjusted to optimize swelling (water capacity), to enhance gloss or to minimize dye migration. For example, the pH of the layer may be reduced to 3.5 to improve swelling capacity, thereby reducing ink drying times, and to impart waterfastness. In another embodiment, the pH of the image recording layer may be raised to 8.5 in order to enhance gloss and reduce bronzing due to surface dye crystallization.
In a preferred embodiment of the invention, the base layer is 50%-100% photographic-grade gelatin, modified so that the pH is far from the isoelectric point of the gelatin, so that water uptake may be maximized. The remainder of the layer may consist of a polymer or inorganic material compatible with the gelatin which does not adversely impact functional properties.
If desired, the base layer of the recording element of the invention may be made porous by the addition of ceramic or hard polymeric particulates, by foaming or blowing during coating, or by inducing phase separation in the layer through introduction of a nonsolvent. In addition, rigidity may be imparted to the base layer through incorporation of a second phase such as polyesters, poly(methacrylates), polyvinyl benzene- containing copolymers and the like.
In the present invention, the recording element can be opaque, translucent, or transparent. Thus, the supports utilized in the recording element of the present invention are not particularly limited and various supports may be employed. Accordingly, plain papers, resin-coated papers, various plastics including a polyester-type resin such as poly(ethylene terephthalate), poly(ethylene naphthalate) and polyester diacetate, a polycarbonate-type resin, a fluorine-type resin such as polytetrafluoroethylene, metal foil, various glass materials, and the like can be employed as supports. When the supports of the present invention are transparent, a transparent recording element can be obtained and used as a transparency in an overhead projector. The thickness of the support employed in the invention can be from about 12 to about 500 xcexcm, preferably from about 75 to about 300 xcexcm.
If desired, in order to improve the adhesion of the base layer to the support, the surface of the support may be corona-discharge-treated prior to applying the base layer or solvent-absorbing layer to the support. Alternatively, an under-coating, such as a layer formed from a halogenated phenol or a partially hydrolyzed vinyl chloride-vinyl acetate copolymer can be applied to the surface of the support.
Since the image recording element may come in contact with other image recording articles or the drive or transport mechanisms of image recording devices, additives such as surfactants, lubricants, matte particles and the like may be added to the element to the extent that they do not degrade the properties of interest.
The layers described above, including the base layer and the top layer, may be coated by conventional coating means onto a support material commonly used in this art. Coating methods may include, but are not limited to, wound wire rod coating, slot coating, slide hopper coating, gravure, curtain coating and the like. Some of these methods allow for simultaneous coatings of both layers, which is preferred from a manufacturing economic perspective.
Ink jet inks used to image the recording elements of the present invention are well-known in the art. The ink compositions used in inkjet printing typically are liquid compositions comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives, and the like. The solvent or carrier liquid can be solely water or can be water mixed with other water-miscible solvents such as polyhydric alcohols. Inks in which organic materials such as polyhydric alcohols are the predominant carrier or solvent liquid may also be used. Particularly useful are mixed solvents of water and polyhydric alcohols. The dyes used in such compositions are typically water-soluble direct or acid type dyes. Such liquid compositions have been described extensively in the prior art including, for example, U.S. Pat. Nos. 4,381,946; 4,239,543 and 4,781,758, the disclosures of which are hereby incorporated by reference.
Although the recording elements disclosed herein have been referred to primarily as being useful for ink jet printers, they also can be used as recording media for pen plotter assemblies. Pen plotters operate by writing directly on the surface of a recording medium using a pen consisting of a bundle of capillary tubes in contact with an ink reservoir.
The following examples further illustrates the invention.